System for generating space frequency block code relay signal and method thereof

ABSTRACT

A method and system for generating a space frequency block code relay signal includes a signal detection unit which detects a received signal by receiving a first and second source signals transmitted from a first and second source nodes, a relay signal generation unit which generates a relay signal cooperating with the first and second source signals using a space frequency block code (SFBC) scheme based on the received signal, and a signal transmitter which transmits the relay signal to a destination node.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No.10-2007-0105265, filed on Oct. 18, 2007, in the Korean IntellectualProperty Office, the entire disclosure of which is incorporated hereinby reference.

TECHNICAL FIELD

The following description relates to a system for generating a spacefrequency block code relay signal in cooperation with a source node, anda method using the system.

BACKGROUND

Low cost technologies for providing Internet services regardless oflocation and time are sought by Internet users and service enterprisers.One scheme for realizing a high speed data transmission rate for mobileInternet users is an Orthogonal Frequency Division Multiplexing (OFDM)scheme.

While OFDM signals are transmitted without being significantly affectedby a frequency-selective fading, OFDM schemes still face various knownproblems. Accordingly, a communication technology using a multi-antennahas attracted a great deal of attention as one of the technologies forsolving the problems of the OFDM scheme.

Since a receiver receiving signals by radio has limitations in terms ofits volume, area, and power consumption, a multi-antenna is generallyequipped in a transmitter. By equipping a plurality of antennas in thetransmitter, it is possible to reduce the complexity of the receiver,and to minimize the performance drop due to a multi-path fading.

However, when a user's mobile terminal is a transmitter, including, butnot limited to, a portable or hand-held terminal, it is difficult toequip the mobile terminal with multiple antennas. To acquire atransmission (TX) diversity effect, the size of a mobile terminal may beincreased to provide sufficient distance between the plurality ofantennas.

Accordingly, there is a need for a system for generating a spacefrequency block code relay signal and a method using the system whichrealizes a high speed data transmission rate and increases frequencyperformance, while meeting the demand for a compact transmitterincluding a user's mobile terminal.

SUMMARY

According to one general aspect, a system for generating a spacefrequency block code relay signal includes: a signal detection unitwhich detects a received signal by receiving first and second sourcesignals transmitted from first and second source nodes; a relay signalgeneration unit which generates a relay signal according to the receivedsignal, wherein the relay signal is generated based on the first andsecond source signals using a space frequency block code (SFBC) scheme;and a signal transmitter which transmits the relay signal to adestination node.

According to another aspect, a method of generating a space frequencyblock code relay signal includes: receiving first and second sourcesignals transmitted from first and second source nodes to detect areceived signal; generating a relay signal according to the receivedsignal, wherein the relay signal is based on the first and second sourcesignals using a space frequency block code (SFBC) scheme; andtransmitting the relay signal to a destination node.

The system and method of generating the space frequency block code relaysignal according to an exemplary embodiment may improve performance of afrequency by generating the space frequency block code relay signalutilizing first and second source signals generated by first and secondsource nodes.

The system and method of generating the space frequency block code relaysignal according to an exemplary embodiment may effectively generate arelay signal with fewer operations by generating the relay signal in atime domain.

According to still another aspect, a system for receiving a spacefrequency block code relay signal includes: a signal detection unitwhich receives first and second source signals transmitted from firstand second source nodes and a relay signal transmitted from a relaynode, and detects a received signal in a frequency domain, the relaysignal being generated using a space frequency block code (SFBC) schemebased on the first and second source signals; an interferencecancellation unit which cancels an interference signal due to anothersource node in the received signal for each of the first and secondsource nodes, and generates first and second interference cancellationsource signals; and a frequency domain equalizer (FDE) which generatesfirst and second compensation source signals by compensating for thefirst and second interference cancellation source signals. Theinterference cancellation unit may cancel the interference occurring dueto the other source node utilizing the first and second compensationsource signals, and update the first and second interferencecancellation source signals.

According to yet another aspect, a method of receiving a space frequencyblock code relay signal includes: receiving first and second sourcesignals transmitted from first and second source nodes and a relaysignal transmitted from a relay node, and detecting a received signal ina frequency domain, the relay signal being generated using a spacefrequency block code (SFBC) scheme based on the first and second sourcesignals; canceling an interference signal due to another source node inthe received signal for each of the first and second source nodes, andgenerating first and second interference cancellation source signals;and generating first and second compensation source signals bycompensating for the first and second interference cancellation sourcesignals.

According to still yet another aspect, a system for generating a relaysignal includes: a signal detection unit which receives first and secondsource signals from first and second source nodes; and a relay signalgeneration unit which generates the relay signal using a space frequencyblock code (SFBC) scheme based on the first and second source signals.The relay signal may be a signal encoded by the SFBC scheme.

According to still a further aspect, a system for generating a spacefrequency block code relay signal includes: a cyclic prefix cancellationunit which cancels a cyclic prefix of first and second source signals;an energy normalization unit which normalizes a received signalcorresponding to the first and second source signals; a serial toparallel converter which separates the received signal normalized to aunit energy signal in a time domain; a discrete Fourier transformer(DFT) which converts the separated unit energy signal into a frequencydomain received signal; an encoding unit comprising a conjugate unit andan order exchange unit which encodes the frequency domain receivedsignal; an inverse discrete Fourier transformer (IDFT) which converts arelay signal in a frequency domain into a signal in a time domain; aparallel to serial converter which integrates the converted signal inthe time domain to generate a relay signal in the time domain; and acyclic prefix adder which adds a cyclic prefix to the replay signal inthe time domain, wherein the relay signal is an encoded signal based onthe first and second source signals using a space frequency block code(SFBC) scheme.

The system and method of receiving the space frequency block code signalmay effectively detect the space frequency block code signal whileimproving the frequency performance.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the present invention will becomeapparent and more readily appreciated from the following detaileddescription of certain exemplary embodiments of the invention, taken inconjunction with the accompanying drawings of which:

FIG. 1 is a diagram illustrating exemplary operations of a first sourcenode, a second source node, a relay node, and a destination node in afirst time slot and a second time slot;

FIG. 2 is a diagram illustrating an exemplary system for generating arelay signal;

FIG. 3 is a block diagram illustrating still another exemplary systemfor generating a space frequency block code relay signal;

FIG. 4 is a diagram illustrating an exemplary system for generating asource signal;

FIG. 5 is a block diagram illustrating an exemplary system for receivinga space frequency block code relay signal;

FIG. 6 is a flowchart illustrating an exemplary method of generating aspace frequency block code relay signal; and

FIG. 7 is a flowchart illustrating an exemplary method of receiving aspace frequency block code relay signal.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The exemplary embodiments are described below in order toexplain the present invention by referring to the figures. The followingdetailed description is provided to assist the reader in gaining acomprehensive understanding of the methods and systems described herein.Accordingly, various changes, modifications, and equivalents of thesystems and methods described herein will be suggested to those ofordinary skill in the art. Also, descriptions of well-known functionsand constructions are omitted to increase clarity and conciseness.

FIG. 1 illustrates operations of a first source node, a second sourcenode, a relay node, and a destination node in a first time slot and asecond time slot.

Referring to FIG. 1, S₁ indicates a first source node, S₂ indicates asecond source node, R indicates a relay node, and D indicates adestination node. In this exemplary embodiment, the first source nodeand the second source node may be mobile terminals, and the destinationnode may be a base station.

The first source node S₁ and the second source node S₂ transmit a firstsource signal x_(S) ₁ and a second source signal x_(S) ₂ to the relaynode R in a first time slot T1. Here, a channel vector of a channelformed between the first source node S1 and the relay node R and achannel formed between the second source node S2 and the relay node Rmay be represented as h_(S) ₁ _(R) and h_(S) ₂ _(R).

The relay node R receives the first source signal x_(S) ₁ and the secondsource signal x_(S) ₂ for the first time slot T1. After a cyclic prefixof the first source signal x_(S) ₁ and the second source signal x_(S) ₂is canceled, a received signal of the relay node R may be representedby,

r _(R)=√{square root over (E _(S) ₁ ^(R))}H _(S) ₁ ^(R) x _(S) ₁+√{square root over (E _(S) ₂ ^(R))}H _(S) ₂ _(R) x _(S) ₂ +w _(R)  [Equation 1]

where H_(S) ₁ _(R) indicates a channel matrix of the channel formedbetween the first source node SI and the relay node R, H_(S) ₂ _(R)indicates a channel matrix of the channel formed between the secondsource node S2 and the relay node R, E_(S) ₁ _(R) indicates effectiveenergy in the relay node R with respect to the first source signal,E_(S) ₂ _(R) indicates effective energy in the relay node R with respectto the second source signal, w_(R) indicates an additive White GaussianNoise whose covariance matrix is σ_(w) ²I_(N), when H_(AB) is N×N, anelement existing in a k^(th) row and an 1^(th) column of H_(AB) is[H_(AB)]_(k,l)=h_(AB)((k−l)mod N), (k−l) mod N indicates a remainder of(k−l) divided by N.

The relay node R generates a relay signal x_(R) based on the receivedsignal r_(R) in a second time slot T2, and transmits the generated relaysignal x_(R) to the destination node D. Here, each of the first sourcenode S₁ and the second source node S₂ transmits the first source signalx_(S) ₁ and the second source signal x_(S) ₂ to the destination node Din the second time slot T2. In this aspect, the relay signal x_(R)cooperates with the first source signal x_(S) ₁ and the second sourcesignal x_(S) ₂ , and is a signal encoded by using a space frequencyblock code (SFBC) scheme. Here, channel vectors of channels formedbetween the relay node R, the first source node S₁, the second sourcenode S₂, and the destination node D may be represented as h_(RD), h_(S)₁ _(D), and h_(S) ₂ _(D).

Therefore, according to an embodiment of the present invention, a highdata-transmission rate may be achieved and performance of a frequencymay be improved via the relay signal x_(R) based on and/or cooperatingwith the first source signal x_(S) ₁ and the second source signal x_(S)₂ . Also, where the first source node S₁ and the second source node S₂are mobile terminals, the high data-transmission rate may be achievedwith a fewer number of antennas.

FIG. 2 illustrates a system for generating a relay signal.

Blocks 210 in FIG. 2 are shown to explain the features of the relaysignal. With reference to FIG. 2, the blocks 210 include a cyclic prefixcancellation unit 211, an energy normalization unit 212, a serial toparallel converter 213, a discrete Fourier transformer (DFT) 214, aconjugate unit 215, an order exchange unit 216, an Inverse DiscreteFourier Transformer (IDFT) 217, a parallel to serial converter (P/S)218, and a cyclic prefix adder 219. It is understood that the blocks 210of FIG. 2 is provided as an illustration, and a system for generating aspace frequency block code relay signal according to an embodiment ofthe present invention may not necessarily include part or all of theblocks 210 shown in FIG. 2.

Referring to FIG. 2, after a cyclic prefix of a first source signalx_(S) ₁ and a second source signal x_(S) ₂ transmitted from a firstsource terminal and a second source terminal is cancelled via the cyclicprefix cancellation unit 211, a received signal r_(R) may be representedas shown in Equation 1.

Here, the received signal r_(R) is normalized to a unity energy whoseenergy size is ‘1’ via the energy normalization unit 212. The unitenergy signal {tilde over (r)}_(R) may be represented by

$\begin{matrix}{{{\overset{\sim}{r}}_{R} = {\frac{r_{R}}{\sqrt{\frac{2}{E_{S_{1}\; R} + E_{S_{1}R} + \sigma_{w}^{2}}}} = {\gamma_{R}r_{R}}}},} & \left\lbrack {{Equation}\mspace{20mu} 2} \right\rbrack\end{matrix}$

where a unit energy signal {tilde over (r)}_(R) is separated via theserial to parallel converter 213 in a time domain, and is converted intoa frequency domain received signal {tilde over (R)}_(R) via the discreteFourier transformer (DFT) 214.

A spectrum corresponding to an even numbered frequency component of thefrequency domain received signal {tilde over (R)}_(R) may be representedas {tilde over (R)}_(R)(2l), and a spectrum corresponding to an oddnumbered frequency component of the frequency domain received signal{tilde over (R)}_(R) may be represented as {tilde over (R)}_(R)(2l+1) Inthis case, l is a whole number ranging from zero to n/2−1.

The frequency domain received signal {tilde over (R)}_(R) may encodedvia the conjugate unit 215 and the order exchange unit 216 as below:

$\begin{matrix}{{\begin{bmatrix}{X_{R}\left( {{2l} + 1} \right)} \\{X_{R}\left( {2l} \right)}\end{bmatrix} = \begin{bmatrix}{- {{\overset{\sim}{R}}_{R}^{*}\left( {{2l} + 1} \right)}} \\{{\overset{\sim}{R}}_{R}^{*}\left( {2l} \right)}\end{bmatrix}},} & \left\lbrack {{Equation}\mspace{20mu} 3} \right\rbrack\end{matrix}$

where l is a whole number ranging from zero to n/2−1.

Referring to Equation. 3, a relay signal in Equation 3 is encodedaccording to a space frequency block code (SFBC) scheme.

Referring again to FIG. 2, a relay signal X_(R) in a frequency domain isconverted into a signal in a time domain via the Inverse DiscreteFourier Transformer (IDFT) 217, and the converted signal in the timedomain is integrated in the time domain via the parallel to serialconverter (P/S) 218 so as to generate a relay signal x_(R) in the timedomain. A cyclic prefix is added to x_(R) by the cyclic prefix adder219.

Consequently, the relay signal X_(R) in the frequency domain withrespect to the finally generated relay signal X_(R) may be representedby,

$\begin{matrix}{\begin{matrix}{x_{R} = {F^{- 1}P\; S\left\{ {F{\overset{\sim}{r}}_{R}} \right\}^{*}}} \\{= {\gamma_{R}\left\{ {{\sqrt{E_{S_{1}R}}F^{- 1}P\; S\left\{ {F\; H_{S_{1}R}x_{1}} \right\}^{*}} +} \right.}} \\{\left. {\sqrt{E_{S_{2}R}}F^{- 1}P\; S\left\{ {F\; H_{S_{2}R}x_{2}} \right\}^{*}} \right\} + w_{R}^{\prime}}\end{matrix}{w_{R}^{\prime} = \frac{\sqrt{2}F^{- 1}P\; S\left\{ {F\; w_{R}} \right\}^{*}}{\sqrt{E_{S_{1}R} + E_{S_{2}R} + N_{0}}}}{S = {I_{\frac{N}{2} \times \frac{N}{2}} \otimes \begin{bmatrix}1 & 0 \\0 & {- 1}\end{bmatrix}}}{{P = {I_{\frac{N}{2} \times \frac{N}{2}} \otimes \begin{bmatrix}0 & 1 \\1 & 0\end{bmatrix}}},}} & \left\lbrack {{Equation}\mspace{20mu} 4} \right\rbrack\end{matrix}$

where F indicates a Fast Fourier Transform matrix,

and indicates a Kronecker product operator.

Here, the system for generating the space frequency block code relaysignal of the present invention may generate the relay signal x_(R) viaoperations in the time domain. Therefore, in Equation 4, the relaysignal x_(R) in the time domain is equivalent to the relay signal X_(R)in the frequency domain, and may be generated via operations in the timedomain, which will be described in detail by referring to FIG. 3.

FIG. 3 illustrates a system for generating a space frequency block coderelay signal according to an exemplary embodiment of the presentinvention.

Referring to FIG. 3, the system includes a signal detection unit 310, arelay signal generation unit 320, and a signal transmitter 330. Thesystem of FIG. 3 is described with reference to embodiments described inrelation to FIGS. 1 and 2.

The signal detection unit 310 detects a received signal r_(R) byreceiving a first source signal x_(S) ₁ and a second source signal x_(S)₂ transmitted from a first source terminal and a second source terminal.The signal detection unit 310 may receive the first source signal x_(S)₁ and the second source signal x_(S) ₂ in a first time slot.

Also, a first source node and a second source node may be scheduledaccording to various schemes. Specifically, the first source node andthe second source node may transmit the first source signal x_(S) ₁ andthe second source signal x_(S) ₂ using the same frequency band for boththe first and second source nodes. The first and second source nodes maybe scheduled using a frequency band whose channel is in good state.Here, a diversity gain may be obtained. Therefore, technical aspects ofthe present invention may be applied to a communication system adoptinga Frequency Division Multiple Access (FDMA) scheme.

The relay signal generation unit 320 generates a relay signal x_(R)based on the first source signal x_(S) ₁ and the second source signalx_(S) ₂ using a space frequency block code scheme. The relay signalx_(R) is based on the received signal r_(R).

Accordingly, even though the first source terminal, the second sourceterminal, and the relay node are separated, the first source terminal,the second source terminal, and the relay node cooperate with each otherand substantially operate as a single transmitter, thereby achieving atransmission diversity effect. In addition, the number of antennasinstalled in the first source terminal and the second source terminalmay be decreased.

The relay signal generation unit 320 may generate the relay signal x_(R)by processing the received signal r_(R) in a time domain. That is, sincethe relay signal generation unit 320 generates the relay signal x_(R) byprocessing the received signal r_(R) in the time domain, operationrequired to generate the relay signal x_(R) may be simplified. Asdescribed in relation to FIG. 2, the relay signal x_(R) may be easilygenerated since the operation of generating the relay signal x_(R) issubstituted with an operation in the time domain.

Accordingly, the relay signal generation unit 320 may calculate aconjugate signal of the received signal r_(R) in the time domain, andgenerate the relay signal x_(R) based on the conjugate signal.

Where a conjugate signal of {tilde over (R)}_(R) is {tilde over(R)}_(R)* in a unit energy signal {tilde over (r)}_(R) and in a unitenergy signal {tilde over (R)}_(R) in the frequency domain, a signal ina time domain corresponding to {tilde over (R)}_(R)* may be representedby,

{tilde over (r)} _(R)(−n)_(N) =r _(C)(n) [Equation 5]

where (A)_(N) indicates a remainder of A divided by N.

That is, by using a symmetry property of the DFT, the signal in the timedomain corresponding to {tilde over (R)}_(R)* may be represented as{tilde over (r)}_(R)*(−n)_(N). The subscript N, for example, (A)_(N)indicates a remainder of A divided by N, and this is a modulo operation.

When both sides of Equation 5 are transformed according to the DFT,Equation 6 may be generated as below:

{tilde over (R)}_(R)*=R_(c)=Wr_(c)   [Equation 6]

where W indicates a root of unity complex multiplicative constants.

Here, each of an odd numbered frequency component and an even numberedfrequency component of {tilde over (R)}_(R)* may be calculated usingD_(e) and D_(o) shown in Equation 7.

D_(e)=[1,0,1,0,1 . . . 1,0,1,0]^(T)

D_(o)=[0,1,0,1 . . . 0,1,0,1]^(T)   [Equation 7]

Specifically, when D_(e) is multiplied by {tilde over (R)}_(R)* orR_(c), the even numbered frequency component of {tilde over (R)}_(R)* orR_(c) may be calculated, and when D_(o) is multiplied by {tilde over(R)}_(R)* or R_(c), the odd numbered frequency component of {tilde over(R)}_(R)* or R_(c) may be calculated.

R _(o)(k)=R _(c)(k)D _(o)(k)

R _(e)(k)=R _(c)(k)D _(e)(k)   [Equation 8]

where k indicates a frequency index.

In Equation 8, since multiplication in the frequency domain may besubstituted with a convolution operation in the time domain, Equation 8may be also represented by,

r _(o)(n)=r _(C)(n)*_(N)δ_(o)(n)

r _(e)(n)=r _(C)(n)*_(N)δ_(e)(n),   [Equation 9]

where *_(N) indicates a circular convolution with respect to a length N.

Since and δ_(e) are δ_(o) zeros except in the case of n=0 or n=N/2,r_(e) and r_(o) may be represented by,

$\begin{matrix}{{{r_{o}(n)} = {{\frac{1}{2}{r_{c}(n)}} + {\frac{1}{2}{r_{c}\left( {n - {N/2}} \right)}_{N}}}}{r_{e}(n)} = {{\frac{1}{2}{r_{c}(n)}} - {\frac{1}{2}{{r_{c}\left( {n - {N/2}} \right)}_{N}.}}}} & \left\lbrack {{Equation}\mspace{20mu} 10} \right\rbrack\end{matrix}$

That is, complex operations in the frequency domain are not necessary tocalculate the odd numbered frequency component R_(o)(k) of {tilde over(R)}_(R)* or R_(c) and the even numbered frequency component of R_(e)(k)of {tilde over (R)}_(R)* or R_(c), and, as shown in Equation 10,r_(o)(n) and r_(e)(n) corresponding to R_(o)(k) and R_(e)(k) may becalculated by performing a conjugation operation, a time shiftoperation, and a convolution operation with respect to {tilde over(r)}_(R).

Therefore, the relay signal x_(R) may be represented using a frequencyshift property as below:

$\begin{matrix}\begin{matrix}{{x_{R}(n)} = {{\frac{1}{2}{r_{c}(n)}\left( {W_{N}^{- n} - W_{N}^{n}} \right)} +}} \\{{\frac{1}{2}{r_{c}\left( {n - {N/2}} \right)}_{N}\left( {W_{N}^{- n} + W_{N}^{n}} \right)}} \\{= {{{r_{c}(n)} \cdot {{jsin}\left( {2\pi \; {n/N}} \right)}} +}} \\{{{r_{c}\left( {n - {N/2}} \right)}_{N} \cdot {{\cos \left( {2\pi \; {n/N}} \right)}.}}}\end{matrix} & \left\lbrack {{Equation}\mspace{20mu} 11} \right\rbrack\end{matrix}$

Consequently, the relay signal generation unit 320 may generate therelay signal x_(R) by performing a conjugation operation, a time shiftoperation, and a convolution operation in the time domain, withoutperforming an operation in the frequency domain, as shown in Equation11.

That is, the operation shown in Equation 4 generating the relay signalX_(R) in the frequency domain may be substituted with the operation asshown in Equation 11 generating the relay signal x_(R) in the timedomain.

The signal transmitter 330 transmits the relay signal x_(R) to adestination node. The signal transmitter 330 may transmit the relaysignal to a destination node in a second time slot. Accordingly, thedestination node may receive the relay signal x_(R), the first sourcesignal x_(S) ₁ , and the second source signal x_(S) ₂ in the second timeslot via a wireless channel, thereby increasing a data transmissionrate.

FIG. 4 illustrates a system for generating a source signal such as afirst source signal and a second source signal.

Referring to FIG. 4, input data is encoded via a forward errorcorrection (FEC) unit 410.

The encoded data is inputted to an interleaver 420, and a burst error istransformed into a random error. The interleaver 420 may interleave in adifferent pattern for each source node.

Also, the interleaved input data may be mapped in various modulationmethods via a symbol mapper 430, and a data symbol may be generated.Specifically, interleaved input data may be mapped into 2^(M)-PhaseShift Keying (PSK) and 2^(M)-Quadrature Amplitude Modulation (QAM)schemes.

Finally, a cyclic prefix is added to the mapped data by a cyclic prefixadder 440.

FIG. 5 illustrates a system for receiving a space frequency block coderelay signal according to an exemplary embodiment of the presentinvention.

Referring to FIG. 5, the system includes a signal detection unit 510, aninterference cancellation unit 520, a frequency domain equalizer (FDE)530, a Fast Fourier Transformer (FFT)/Inverse Fast Fourier Transformer(IFFT) 540, a decoding unit 550, an interleaver 560, a soft mapper 570,and a space frequency block code (SFBC) encoder 580.

The signal detection unit 510 receives a first source signal x_(S) ₁ andsecond source signal x_(S) ₂ transmitted from a first and second sourcenodes and a relay signal x_(R) transmitted from a relay node, anddetects a received signal in a frequency domain.

A received signal r_(D) in a time domain, having a cyclic prefixcancelled via a prefix cancellation unit 511, is transformed into areceived signal in a frequency domain via a Fast Fourier Transformer512. In this instance, the received signal r_(D) in the time domain maybe represented using Equation 12,

$\begin{matrix}\begin{matrix}{r_{D} = {{\sqrt{E_{S_{1}R}}H_{S_{1}D}x_{1}} + {\sqrt{E_{S_{2}D}}H_{S_{2}D}x_{2}} +}} \\{{{\sqrt{E_{R\; D}}H_{R\; D}x_{R}} + w_{D}}} \\{= {{\sqrt{E_{S_{1}R}}H_{S_{1}D}x_{1}} +}} \\{{{\gamma_{R}\sqrt{E_{R\; D}E_{S_{1}R}}H_{R\; D}F^{- 1}P\; S\left\{ {F\; H_{S_{1}R}x_{1}} \right\}^{*}} +}} \\{{{\sqrt{E_{S_{2}D}}H_{S_{2}D}x_{2}} +}} \\{{{\gamma_{R}\sqrt{E_{R\; D}E_{S_{2}R}}H_{R\; D}F^{- 1}P\; S\left\{ {F\; H_{S_{2}R}x_{2}} \right\}^{*}} +}} \\{{{{\sqrt{E_{R\; D}}H_{R\; D}w_{R}^{\prime}} + w_{D}},}}\end{matrix} & \left\lbrack {{Equation}\mspace{20mu} 12} \right\rbrack\end{matrix}$

where W_(D) indicates is a complex additive White Gaussian Noise whoseaverage is zero, and dispersion is σ_(w) ².

Here, a portion of the second row and the fourth row in Equation 12 maybe represented by,

$\begin{matrix}{\begin{matrix}{{H_{R\; D}F^{- 1}P\; S\left\{ {F\; H_{S_{u}R}x_{u}} \right\}^{*}} = {F^{- 1}\Lambda_{R\; D}P\; S\; \Lambda_{S_{u}R}^{*}\left\{ {F\; x_{u}} \right\}^{*}}} \\{= {F^{- 1}\Lambda_{R\; D}P\; \Lambda_{S_{u}R}^{*}S\left\{ {F\; x_{u}} \right\}^{*}}} \\{\cong {F^{- 1}\Lambda_{R\; D}\; \Lambda_{S_{u}R}^{*}P\; S\left\{ {F\; x_{u}} \right\}^{*}}}\end{matrix}{\Lambda_{S_{u}R} = {F\; H_{S_{u}R}F^{- 1}}}{\Lambda_{R\; D} = {F\; H_{R\; D}{F^{- 1}.}}}} & \left\lbrack {{Equation}\mspace{20mu} 13} \right\rbrack\end{matrix}$

where u indicates an index of a first source terminal and a secondsource terminal, and is 1 or 2.

In Equation 13, frequency responses between adjacent sub channels arealmost the same with each other.

The r_(D) ¹ which is a normalized r_(D) of Equation 12 may berepresented by,

$\begin{matrix}{{r_{D}^{\prime} = {{\gamma_{S_{1}D}H_{S_{1}D}x_{1}} + {\gamma_{S_{2}D}H_{S_{2}D}x_{2}} + {\gamma_{S_{1}R\; D}F^{- 1}\Lambda_{S_{1}R\; D}P\; S\left\{ {F\; x_{1}} \right\}^{*}} + {\gamma_{S_{2}R\; D}F^{- 1}\Lambda_{S_{2}R\; D}P\; S\left\{ {F\; x_{2}} \right\}^{*}} + w}}\mspace{20mu} {\gamma_{S_{u}D} = {\eta \sqrt{E_{S_{u}D}\left( {E_{S_{1}R} + E_{S_{2}R} + \sigma_{w}^{2}} \right)}}}\mspace{20mu} {\gamma_{S_{u}R\; D} = {\eta \sqrt{2E_{S_{u}R}E_{R\; D}}}}\mspace{20mu} {w = {\eta \sqrt{E_{S_{1}R} + E_{S_{2}R} + \sigma_{w}^{2}}\left( {w_{D} + {\sqrt{E_{R\; D}}H_{R\; D}w_{R}^{\prime}}} \right)}}\mspace{20mu} {{\eta = \sqrt{\frac{1}{E_{S_{1}R} + E_{S_{2}R} + \sigma_{w}^{2} + {2E_{R\; D}{\sum\limits_{l = 0}^{L_{R\; D}}{{h_{R\; D}(l)}}^{2}}}}}},}} & \left\lbrack {{Equation}\mspace{20mu} 14} \right\rbrack\end{matrix}$

where L_(AB) indicates a channel memory length of a channel formedbetween an A node and a B node, and is related to an time length of achannel impulse response.

The r_(D) ¹ is transformed into a received signal R_(D) ¹ in thefrequency domain via the FFT 512. R_(D) ¹ may be represented by,

$\begin{matrix}{R_{D}^{\prime} = {{\gamma_{S_{1}D}\Lambda_{S_{1}D}X_{1}} + {\gamma_{S_{2}D}\Lambda_{S_{2}D}X_{2}} + {\gamma_{S_{1}R\; D}\Lambda_{S_{1}R\; D}P\; S\; X_{1}^{*}} + {\gamma_{S_{2}R\; D}\Lambda_{S_{2}R\; D}P\; S\; X_{2}^{*}} + {W.}}} & \left\lbrack {{Equation}\mspace{20mu} 15} \right\rbrack\end{matrix}$

Accordingly, the signal detection unit 510 may detect R_(D) ¹.

Also, the interference cancellation unit 520 cancels an interferencesignal occurring due to another source node in the received signal foreach of the first and second source nodes, and generates first andsecond interference cancellation source signals.

With respect to R_(D) ¹, where a first interference cancellation sourcesignal generated by cancellation of an interference signal occurring dueto a second source terminal for the first source terminal is Z₁, and asecond interference cancellation source signal generated by cancellationof an interference signal occurring due to a first source terminal forthe second source terminal is Z₂, Z₁ and Z₂ may be represented by,

$\begin{matrix}{{Z_{1} = {{\gamma_{S_{1}D}\Lambda_{S_{1}D}X_{1}} + {\gamma_{S_{1}R\; D}\Lambda_{S_{1}R\; D}P\; S\; X_{1}^{*}} + {\gamma_{S_{2}D}{\Lambda_{S_{2}D}\left( {X_{2} - {\overset{\_}{X}}_{2}} \right)}} + {\gamma_{S_{2}R\; D}\Lambda_{S_{2}R\; D}P\; {S\left( {X_{2}^{*} - {\overset{\_}{X}}_{2}^{*}} \right)}} + W}}{{Z_{2} = {{\gamma_{S_{1}D}{\Lambda_{S_{1}D}\left( {X_{1} - {\overset{\_}{X}}_{1}} \right)}} + {\gamma_{S_{1}R\; D}\Lambda_{S_{1}R\; D}P\; {S\left( \; {X_{1}^{*} - {\overset{\_}{X}}_{1}^{*}} \right)}} + {\gamma_{S_{2}D}\Lambda_{S_{2}D}X_{2}} + {\gamma_{S_{2}R\; D}\Lambda_{S_{2}R\; D}P\; S\; X_{2}^{*}} + W}},}} & \left\lbrack {{Equation}\mspace{20mu} 16} \right\rbrack\end{matrix}$

where X _(u) indicates an average vector with respect to the decodedu^(th) source signal in the frequency domain.

That is, referring to Equation 16, the interference cancellation unit520 repeatedly cancels the interference signal in R_(D) ¹, and generatesthe first interference cancellation source signal corresponding to thefirst source signal and the second interference cancellation sourcesignal corresponding to the second source signal. In particular, as anumber of the repeated cancellation by the interference cancellationunit 520 is increased, the first and second interference source signalswhose interference is nearly canceled in R_(D) ¹ may be obtained.

Also, the frequency domain equalizer (FDE) 530, including an SBFCcombiner 531 and an 1-tap MMSE FDE (Minimum Mean Square Error FrequencyDomain Equalizer) 532, generates a first compensation source signalcorresponding to the first source signal and a second compensationsource signal corresponding to the second source signal by compensatingfor the first and second interference cancellation source signals.

That is, Z_(u)(Z₁, Z₂) is inputted to the an SBFC combiner 531. Withregard to Z₁, after a complex conjugate is performed with respect to Z₁,Equation 17 in a matrix type may be calculated.

$\begin{matrix}{\begin{matrix}{Z_{l,k}^{\prime} = \begin{bmatrix}{Z_{l}^{\prime}\left( {2k} \right)} \\{Z_{l}^{*\prime}\left( {{2k} + 1} \right)}\end{bmatrix}} \\{= {{\begin{bmatrix}{\Lambda_{S_{1}\; D}^{\prime}\left( {2k} \right)} & {- {\Lambda_{S_{1}R\; D}^{\prime}\left( {2k} \right)}} \\{\Lambda_{S_{1}R\; D}^{\prime*}\left( {2k} \right)} & {\Lambda_{S_{1}D}^{\prime*}\left( {2k} \right)}\end{bmatrix}\begin{bmatrix}{X_{l}\left( {2k} \right)} \\{X_{l}^{*}\left( {{2k} + 1} \right)}\end{bmatrix}} +}} \\{\begin{bmatrix}{\Lambda_{S_{2}\; D}^{\prime}\left( {2k} \right)} & {- {\Lambda_{S_{2}R\; D}^{\prime}\left( {2k} \right)}} \\{\Lambda_{S_{2}R\; D}^{\prime*}\left( {2k} \right)} & {\Lambda_{S_{2}D}^{\prime*}\left( {2k} \right)}\end{bmatrix}} \\{{\begin{bmatrix}{{X_{2}\left( {2k} \right)} - {{\overset{\_}{X}}_{2}\left( {2k} \right)}} \\{{X_{2}^{*}\left( {{2k} + 1} \right)} - {{\overset{\_}{X}}_{2}^{*}\left( {{2k} + 1} \right)}}\end{bmatrix} +}} \\{\begin{bmatrix}{W\left( {2k} \right)} \\{W^{*}\left( {{2k} + 1} \right)}\end{bmatrix}} \\{\equiv {{\Lambda_{l,k}X_{l,k}^{\prime}} + {\Lambda_{2,k}X_{2,k}^{\prime}} + W^{\prime}}}\end{matrix}{{\Lambda_{S_{u}D}^{\prime}\left( {2k} \right)} = {\gamma_{S_{u}D}{\Lambda_{S_{u}D}\left( {2k} \right)}}}{{{\Lambda_{S_{u}R\; D}^{\prime}\left( {2k} \right)} = {\gamma_{S_{u}R\; D}{\Lambda_{S_{u}R\; D}\left( {2k} \right)}}},}} & \left\lbrack {{Equation}\mspace{20mu} 17} \right\rbrack\end{matrix}$

After Z₁ is SFBC combined, the signal may be represented by,

$\begin{matrix}{\begin{matrix}{\mspace{79mu} {{\overset{\sim}{Z}}_{1,k}^{\prime} = {\begin{bmatrix}{{\overset{\sim}{Z}}_{1}^{\prime}\left( {2k} \right)} \\{{\overset{\sim}{Z}}_{1}^{\prime}\left( {{2k} + 1} \right)}\end{bmatrix} = {\Lambda_{1,k}^{H}Z_{1,k}^{\prime}}}}} \\{= {{\begin{bmatrix}{\Lambda_{1}\left( {2k} \right)} & 0 \\0 & {\Lambda_{1}\left( {2k} \right)}\end{bmatrix}\begin{bmatrix}{X_{l}\left( {2k} \right)} \\{X_{l}^{*}\left( {{2k} + 1} \right)}\end{bmatrix}} +}} \\{\begin{bmatrix}{{\overset{\Cup}{A}}_{2}\left( {2k} \right)} & {- {{\overset{\Cup}{B}}_{2}\left( {2k} \right)}} \\{{\overset{\Cup}{C}}_{2}\left( {2k} \right)} & {{\overset{\Cup}{D}}_{2}\left( {2k} \right)}\end{bmatrix}} \\{{\begin{bmatrix}{{X_{2}\left( {2k} \right)} - {{\overset{\_}{X}}_{2}\left( {2k} \right)}} \\{{X_{2}^{*}\left( {{2k} + 1} \right)} - {{\overset{\_}{X}}_{2}^{*}\left( {{2k} + 1} \right)}}\end{bmatrix} +}} \\{{\Lambda_{1,k}^{H}\begin{bmatrix}{W\left( {2k} \right)} \\{W^{*}\left( {{2k} + 1} \right)}\end{bmatrix}}}\end{matrix}\mspace{79mu} {{{\overset{\sim}{\Lambda}}_{1}\left( {2k} \right)} = {{{\Lambda_{S_{1}D}^{\prime}\left( {2k} \right)}}^{2} + {{\Lambda_{S_{1}R\; D}^{\prime}\left( {2k} \right)}}^{2}}}{{{\overset{\Cup}{A}}_{2}\left( {2k} \right)} = {{{{\Lambda_{S_{1}D}^{\prime}\left( {2k} \right)}{\Lambda_{S_{2}D}^{\prime}\left( {2k} \right)}} + {{\Lambda_{S_{1}R\; D}^{\prime*}\left( {2k} \right)}{\Lambda_{S_{2}R\; D}^{\prime*}\left( {2k} \right)}}} = {{\overset{\Cup}{D}}_{2}\left( {2k} \right)}}}{{{\overset{\Cup}{B}}_{2}\left( {2k} \right)} = {{{{- {\Lambda_{S_{1}D}^{\prime*}\left( {2k} \right)}}{\Lambda_{S_{2}R\; D}^{\prime*}\left( {2k} \right)}} + {{\Lambda_{S_{1}R\; D}^{\prime}\left( {2k} \right)}{\Lambda_{S_{2}\; D}^{\prime*}\left( {2k} \right)}}} = {- {{\overset{\Cup}{C}}_{2}\left( {2k} \right)}}}}} & \left\lbrack {{Equation}\mspace{20mu} 18} \right\rbrack\end{matrix}$

Referring to Equation {tilde over (Z)}₁′(2k) and {tilde over(Z)}₁′(2k+1) may be represented by,

$\begin{matrix}{{{{\overset{\sim}{Z}}_{1}^{\prime}\left( {2k} \right)} = {{{{\overset{\sim}{\Lambda}}_{1}\left( {2k} \right)}{X_{1}\left( {2k} \right)}} + {{{\overset{\Cup}{A}}_{2}\left( {2k} \right)}\left( {{X_{2}\left( {2k} \right)} - {{\overset{\_}{X}}_{2}\left( {2k} \right)}} \right)} + {{{\overset{\Cup}{B}}_{2}\left( {2k} \right)}\left( {{X_{2}^{*}\left( {{2k} + 1} \right)} - {{\overset{\_}{X}}_{2}^{*}\left( {{2k} + 1} \right)}} \right)} + {{\Lambda_{S_{1}D}^{\prime*}\left( {2k} \right)}{W\left( {2k} \right)}} + {{\Lambda_{S_{1}R\; D}^{\prime \;}\left( {2k} \right)}{W^{*}\left( {{2k} + 1} \right)}}}}{{{\overset{\sim}{Z}}_{1}^{\prime}\left( {{2k} + 1} \right)} = {{{{\overset{\sim}{\Lambda}}_{1}\left( {2k} \right)}{X_{1}^{*}\left( {{2k} + 1} \right)}} - {{{\overset{\Cup}{B}}_{2}\left( {2k} \right)}\left( {{X_{2}\left( {2k} \right)} - {{\overset{\_}{X}}_{2}\left( {2k} \right)}} \right)} + {{{\overset{\Cup}{A}}_{2}\left( {2k} \right)}\left( {{X_{2}^{*}\left( {{2k} + 1} \right)} - {{\overset{\_}{X}}_{2}^{*}\left( {{2k} + 1} \right)}} \right)} - {{\Lambda_{S_{1}R\; D}^{\prime*}\left( {2k} \right)}{W\left( {2k} \right)}} + {{\Lambda_{S_{1}D}^{\prime \;}\left( {2k} \right)}{W^{*}\left( {{2k} + 1} \right)}}}}} & \left\lbrack {{Equation}\mspace{20mu} 19} \right\rbrack\end{matrix}$

Also, the 1-tap MMSE FDE 532 may compensate {tilde over (Z)}₁′(2k) and{tilde over (Z)}₁′(2k+1) using an equalization coefficient shown inEquation 20.

$\begin{matrix}{\begin{matrix}{{G_{1}\left( {2k} \right)} = {G_{1}\left( {{2k} + 1} \right)}} \\{= \frac{{\overset{\sim}{\Lambda}}_{1}\left( {2k} \right)}{\begin{matrix}{{v_{1}{{{\overset{\sim}{\Lambda}}_{1}\left( {2k} \right)}}^{2}} + {v_{2}{{{\overset{\Cup}{A}}_{2}\left( {2k} \right)}}^{2}} +} \\{{v_{2}{{{\overset{\Cup}{B}}_{2}\left( {2k} \right)}}} + {\sigma_{w}^{2}{{\overset{\sim}{\Lambda}}_{1}\left( {2k} \right)}}}\end{matrix}}}\end{matrix}{{v_{u} = {\frac{1}{N}{trace}\mspace{11mu} \left( V_{u} \right)}},}} & \left\lbrack {{Equation}\mspace{20mu} 20} \right)\end{matrix}$

, where trace (X) indicates a set of diagonal elements of X, and

$\begin{matrix}{V_{u} = {{covariance}\mspace{11mu} \left( {x_{u}x_{u}} \right)}} \\{= {{Diagonal}\mspace{11mu} {\left( {v_{u,0},v_{u,1},\ldots \mspace{11mu},v_{u,{N - 1}}} \right).}}}\end{matrix}$

Consequently, the first compensation source signal which is generatedafter the first interference cancellation source signal passes throughthe SBFC combiner 531 and the 1-tap MMSE FDE 532 may be represented by,

$\begin{matrix}{{{{\overset{\Cap}{X}}_{1}\left( {2k} \right)} = {{{G_{`1}^{*}\left( {2k} \right)}{{\overset{\sim}{Z}}_{1}^{\prime}\left( {2k} \right)}} + {\left( {\mu_{1} - {{G_{1}^{*}\left( {2k} \right)}{{\overset{\sim}{\Lambda}}_{1}\left( {2k} \right)}}} \right){{\overset{\_}{X}}_{1}\left( {2k} \right)}}}}{{{\overset{\Cap}{X}}_{1}^{*}\left( {{2k} + 1} \right)} = {{{G_{`1}^{*}\left( {{2k} + 1} \right)}{{\overset{\sim}{Z}}_{1}^{\prime}\left( {{2k} + 1} \right)}} + {\left( {\mu_{1} - {{G_{1}^{*}\left( {{2k} + 1} \right)}{{\overset{\sim}{\Lambda}}_{1}\left( {{2k} + 1} \right)}}} \right){{\overset{\_}{X}}_{1}^{*}\left( {{2k} + 1} \right)}}}}\mspace{20mu} {\mu_{1} = {\frac{l}{N}{\sum\limits_{k = 0}^{N - 1}\left( {{G_{1}^{*}(k)}{{\overset{\sim}{\Lambda}}_{1}(k)}} \right)}}}\mspace{20mu} {\sigma_{1}^{2} = {\mu_{1} - {v_{1}\mu_{1}^{2}}}}} & \left\lbrack {{Equation}\mspace{20mu} 21} \right\rbrack\end{matrix}$

where μ₁ indicates an average with respect to an estimate of the firstsource signal in a time domain, and σ₁ indicates dispersion with respectto an estimate of the first source signal in a time domain.

Since an average and dispersion with respect to the second compensationsource signal in the time domain may be generated via the abovedescribed algorithm, descriptions regarding generation of the secondcompensation source signal are omitted.

The first compensation source signal and the second compensation sourcesignal generated via the frequency domain equalizer 530 are transformedinto signals in the time domain via the FFT/IFFT 540.

Also, the first compensation source signal and the second compensationsource signal which are transformed into signals in the time domain aredecoded via the decoding unit 550.

Here, extrinsic log likelihood ratios (LLRs) may be generated usingEquation 22, as below:

$\begin{matrix}{{{L_{E}\left( {c_{u}\left( {2n} \right)} \right)} = \frac{2\sqrt{2}{Re}\left\{ {\overset{\Cap}{x}(n)} \right\} \mu_{u}}{\sigma_{u}^{2}}}{{L_{E}\left( {c_{u}\left( {{2n} + 1} \right)} \right)} = {\frac{2\sqrt{2}{Im}\; \left\{ {\overset{\Cap}{x}(n)} \right\} \mu_{u}}{\sigma_{u}^{2}}.}}} & \left\lbrack {{Equation}\mspace{20mu} 22} \right\rbrack\end{matrix}$

Also, a first estimation source signal corresponding to the first sourcesignal and a second estimation source signal corresponding to the secondsource signal are generated via the decoder 553. The first and secondestimation source signals are decoded first and second source signals inthe time domain, the signals of which interference is cancelled.

A maximum a posteriori (MAP) detector 551 decides on the first andsecond compensation source signals which have been transformed intosignals in the time domain.

Also, an inverse interleaver 552 reconstructs interleaved signals usinga pattern respectively corresponding to the first and second sourcesignals.

After passing through the inverse interleaver 552, a priori LLR withrespect to the reconstructed signals may be represented by Equation 22,as below:

$\begin{matrix}{\left\{ {L_{D\; A}\left( {c_{u}(l)} \right)} \right\}_{l = 0}^{{M\; N} - 1} = {{\pi_{u}^{- 1}\left( \left\{ {L_{E}\left( {c_{u}\left( {2m} \right)} \right)} \right\}_{m = 0}^{{M\; N} - 1} \right)}.}} & \left\lbrack {{Equation}\mspace{20mu} 23} \right\rbrack\end{matrix}$

The decoder 553 calculates extrinsic information with respect to codeddata and decoded data using a priori LLR, and feeds back the calculatedextrinsic information to the interference cancellation unit 520 and the1-tap MMSE FDE 532. The extrinsic information may be used as prioriinformation in the interference cancellation unit 520 and the 1-tap MMSEFDE 532.

The decoder 553 generates a first estimation source signal, a decodedfirst compensation source signal, corresponding to the first sourcesignal, and a second estimation source signal, a decoded secondcompensation source signal, corresponding to the second source signal.

The first and second estimation source signals are re-interleaved viathe interleaver 560. Also, the interleaved first and second estimationsource signals are re-mapped into data symbols via a soft mapper 570.Here, the interleaver 560 may use the same interleaving pattern as thefirst source terminal and the second source terminal, and the softmapper 570 may use the same mapping method as the first source terminaland the second source terminal.

Accordingly, after the first and second estimation source signals areinterleaved, signals generated by being mapped into data symbols areencoded via the SFBC encoder 580. The encoded signals are fed back tothe interference cancellation unit 520, and the interferencecancellation unit 520 updates the first and second interferencecancellation signals using the fed back signals.

As described above, the interference cancellation unit 520 repeatedlycancels interference, the frequency domain equalizer 530 performsequalization, and the decoding unit 550 repeatedly performs decoding,thereby acquiring the first and second estimation source signals whichare nearly the same as the first and second source signals.

FIG. 6 is a flowchart illustrating a method of generating a spacefrequency block code relay signal according to an exemplary embodimentof the present invention.

With reference to FIG. 6, the method comprises detecting a receivedsignal by receiving a first and second source signals being transmittedfrom a first and second source nodes, in operation S610, and generatinga relay signal according to the received signal based on the first andsecond source signals and a space frequency block code (SFBC) scheme, inoperation S620.

According to one aspect of the present invention, in operation S620, thereplay signal may be generated by processing the received signal in atime domain.

According to another aspect, in operation S620, a conjugate signal ofthe received signal in the time domain may be calculated, and the relaysignal may be generated based on the conjugate signal of the receivedsignal.

According to still another aspect, in operation S620, the relay signalmay be generated by performing a conjugation operation, a time shiftoperation, and a convolution operation with respect to the receivedsignal in the time domain.

The method may further comprise transmitting the relay signal to adestination node in operation S630.

FIG. 7 is a flowchart illustrating a method of receiving a spacefrequency block code relay signal according to an exemplary embodimentof the present invention.

With reference to FIG. 7, the method comprises, receiving first andsecond source signals being transmitted from first and second sourcenodes and a relay signal being transmitted from a relay node, anddetecting a received signal in a frequency domain, in operation S710,canceling an interference signal occurring due to another source node inthe received signal for each of the first and second source nodes, andgenerating first and second interference cancellation source signals, inoperation S720, and generating a first and second compensation sourcesignals by compensating for the first and second interferencecancellation source signals, in operation S730.

According to one aspect of the present invention, the operation S720 ofgenerating the first and second interference cancellation source signalsmay update the first and second interference cancellation source signalsby canceling the interference due to the other source node utilizing thefirst and second compensation source signals.

According to another aspect, the operation S730 of generating the firstand second compensation source signals may generate the first and secondcompensation source signals according to an equalization coefficientwhich is generated based on a channel state of channels formed betweenthe first node, the second node, the relay node, and a base station.

According to still another aspect, the operation S730 of generating thefirst and second compensation source signals may generate the first andsecond compensation source signals based on the equalization coefficientwhich is generated according to a minimum mean square error (MMSE)scheme.

Since some of the descriptions relating to FIGS. 1 through 5 may beapplicable to FIGS. 6 and 7, those descriptions for FIGS. 6 and 7 willbe omitted for conciseness.

The method of generating and receiving a space frequency block coderelay signal according to the above-described exemplary embodiments maybe recorded, stored, or fixed in one or more computer-readable mediathat include program instructions to be implemented by a computer tocause a processor to execute or perform the program instructions. Themedia may also include, alone or in combination with the programinstructions, data files, data structures, and the like. Examples ofcomputer-readable media include magnetic media, such as hard disks,floppy disks, and magnetic tape; optical media such as CD ROM disks andDVD; magneto-optical media, such as optical disks; and hardware devicesthat are specially configured to store and perform program instructions,such as read-only memory (ROM), random access memory (RAM), flashmemory, and the like. The media may also be a transmission medium suchas optical or metallic lines, wave guides, and the like, including acarrier wave transmitting signals specifying the program instructions,data structures, and the like. Examples of program instructions includeboth machine code, such as produced by a compiler, and files containinghigher level code that may be executed by the computer using aninterpreter. The described hardware devices may be configured to act asone or more software modules in order to perform the operations of theabove-described embodiments of the present invention.

Although a few exemplary embodiments of the present invention have beenshown and described, the present invention is not limited to thedescribed exemplary embodiments. Instead, it would be appreciated bythose skilled in the art that changes may be made to these exemplaryembodiments without departing from the principles and spirit of theinvention, the scope of which is defined by the claims and theirequivalents.

1. A system for generating a space frequency block code relay signal,the system comprising: a signal detection unit which detects a receivedsignal by receiving first and second source signals transmitted fromfirst and second source nodes; a relay signal generation unit whichgenerates a relay signal according to the received signal, wherein therelay signal is generated based on the first and second source signalsusing a space frequency block code (SFBC) scheme; and a signaltransmitter which transmits the relay signal to a destination node. 2.The system of claim 1, wherein the relay signal generation unitgenerates the relay signal by processing the received signal in a timedomain.
 3. The system of claim 1, wherein the relay signal generationunit calculates a conjugate signal of the received signal in a timedomain, and generates the relay signal based on the conjugate signal ofthe received signal.
 4. The system of claim 1, wherein the relay signalgeneration unit generates the relay signal by performing a conjugationoperation, a time shift operation, and a convolution operation withrespect to the received signal in a time domain.
 5. The system of claim1, wherein the signal detection unit receives the first and secondsource signals in a first time slot, and the signal transmittertransmits the relay signal to the destination node in a second timeslot.
 6. The system of claim 1, wherein the first and second sourcenodes are mobile terminals, and the destination node is a base station.7. The system of claim 1, wherein the signal detection unit detects thereceived signal by receiving the first and second source signals beingtransmitted using the same frequency band for both the first and secondsource nodes.
 8. A system for receiving a space frequency block coderelay signal, the system comprising: a signal detection unit whichreceives first and second source signals transmitted from first andsecond source nodes and a relay signal transmitted from a relay node,and detects a received signal in a frequency domain, the relay signalbeing generated using a space frequency block code (SFBC) scheme basedon the first and second source signals; an interference cancellationunit which cancels an interference signal due to another source node inthe received signal for each of the first and second source nodes, andgenerates first and second interference cancellation source signals; anda frequency domain equalizer (FDE) which generates first and secondcompensation source signals by compensating for the first and secondinterference cancellation source signals.
 9. The system of claim 8,wherein the frequency domain equalizer (FDE) generates the first andsecond compensation source signals according to an equalizationcoefficient which is generated based on a channel state of channelsformed between the first source node, the second source node, the relaynode, and a base station.
 10. The system of claim 9, wherein thefrequency domain equalizer (FDE) generates the first and secondcompensation source signals based on the equalization coefficient whichis generated according to a minimum mean square error (MMSE) scheme. 11.The system of claim 24, further comprising: a decoder unit whichconverts the first and second compensation source signals to signals ina time domain, and generates first and second estimation source signalsby decoding the first and second compensation source signals in the timedomain, wherein the interference cancellation unit updates the first andsecond interference cancellation source signals based on the first andsecond estimation source signals.
 12. The system of claim 8, wherein thesignal detection unit receives the first and second source signals beingtransmitted from the first and second source nodes using the samefrequency band for both the first and second source nodes and the relaysignal being transmitted from the relay node, and detects the receivedsignal in the frequency domain.
 13. A method of generating a spacefrequency block code relay signal, the method comprising: receivingfirst and second source signals transmitted from first and second sourcenodes so as to detect a received signal; generating a relay signalaccording to the received signal, wherein the relay signal being basedon the first and second source signals using a space frequency blockcode (SFBC) scheme; and transmitting the relay signal to a destinationnode.
 14. The method of claim 13, wherein the generating of the relaysignal comprises generating the relay signal by processing the receivedsignal in a time domain.
 15. The method of claim 13, wherein thegenerating of the relay signal comprises generating the relay signalbased on a conjugate signal of the received signal in a time domain. 16.The method of claim 13, wherein the generating of the relay signalcomprises generating the relay signal by performing a conjugationoperation, a time shift operation, and a convolution operation withrespect to the received signal.
 17. The method of claim 13, wherein: thedetecting of the received signal comprises receiving the first andsecond source signals in a first time slot, and the transmitting of therelay signal comprises transmitting the relay signal to the destinationnode in a second time slot.
 18. A method of receiving a space frequencyblock code signal, the method comprising: receiving first and secondsource signals transmitted from first and second source nodes and arelay signal transmitted from a relay node, and detecting a receivedsignal in a frequency domain, the relay signal being generated using aspace frequency block code (SFBC) scheme based on the first and secondsource signals; canceling an interference signal due to another sourcenode in the received signal for each of the first and second sourcenodes, and generating first and second interference cancellation sourcesignals; and generating first and second compensation source signals bycompensating for the first and second interference cancellation sourcesignals.
 19. The method of claim 18, wherein the generating of the firstand second compensation source signals comprises generating the firstand second compensation source signals according to an equalizationcoefficient based on a channel state of a channel formed between thefirst source node, the second source node, the relay node, and a basestation.
 20. The method of claim 19, wherein the generating of the firstand second compensation source signals comprises generating the firstand second compensation source signals based on an equalizationcoefficient generated according to a minimum mean square error (MMSE)scheme.
 21. At least one computer-readable storage medium storinginstructions for implementing the method of claim
 13. 22. The system ofclaim 1, wherein the system is operative in a communication systemadopting a Frequency Division Multiple Access (FDMA) scheme.
 23. Thesystem of claim 1, wherein the first and second source signals are dataencoded by a forward error correction (FEC) unit, interleaved by aninterleaver, mapped by a symbol mapper, and provided with a cyclicprefix by a cyclic prefix adder.
 24. The system of claim 8, wherein theinterference cancellation unit cancels the interference due to the othersource node by utilizing the first and second compensation sourcesignals, and updates the first and second interference cancellationsource signals.
 25. The system of claim 8, further comprising: a fastFourier transformer (FFT)—inverse fast Fourier transformer (IFFT) whichtransforms the first and second compensation source signals into signalsin a time domain; a decoding unit which decodes the signals in the timedomain, wherein the decoding unit comprises: a maximum a posteriori(MAP) detector which decides on the first and second compensation sourcesignals transformed into the time domain, an inverse interleaver whichreconstructs interleaved signals using a pattern respectivelycorresponding to the first and second source signals, and a decoderwhich generates first and second estimation source signals correspondingto the first and second source signals; an interleaver whichre-interleaves the first and second estimation source signals; a softmapper which re-maps the interleaved first and second estimation sourcesignals into data symbols; and a space frequency block code (SFBC)encoder which encodes signals generated by being mapped into the datasymbols.
 26. The system of claim 25, wherein the interferencecancellation unit updates the first and second interference cancellationsignals using the encoded signals from the SFBC encoder.
 27. The methodof claim 18, wherein the cancelling of the interference signal comprisescancelling the interference signal by utilizing the first and secondcompensation source signals, and generating of the first and secondinterference cancellation source signals comprises updating the firstand second interference cancellation source signals.
 28. The method ofclaim 27, further comprising converting the first and secondcompensation source signals to signals in a time domain, and generatingfirst and second estimation source signals by decoding the first andsecond compensation source signals in the time domain, wherein theupdating of the first and second interference cancellation sourcesignals comprises updating of the first and second interferencecancellation source signals based on the first and second estimationsource signals.
 29. At least one computer-readable storage mediumstoring instructions for implementing the method of claim
 18. 30. Asystem for generating a space frequency block code relay signal, thesystem comprising: a cyclic prefix cancellation unit which cancels acyclic prefix of first and second source signals; an energynormalization unit which normalizes a received signal corresponding tothe first and second source signals; a serial to parallel converterwhich separates the received signal normalized to a unit energy signal,in a time domain; a discrete Fourier transformer (DFT) which convertsthe separated unit energy signal into a frequency domain receivedsignal; an encoding unit comprising a conjugate unit and an orderexchange unit, which encodes the frequency domain received signal; aninverse discrete Fourier transformer (IDFT) which converts a relaysignal in a frequency domain into a signal in a time domain; a parallelto serial converter which integrates the converted signal in the timedomain to generate a relay signal in the time domain; and a cyclicprefix adder which adds a cyclic prefix to the replay signal in the timedomain, wherein the relay signal is an encoded signal based on the firstand second source signals using a space frequency block code (SFBC)scheme.